# Planetary Gear, high torque, low output speed System

• posted

An honest application:

Needed torque at output: 2500 in.lbs. (give or take a little - ok) Output speed: 4 rpm (give or take a little - ok) Reversable Self-locking Duty-cycle: a few times a day running one-two minutes. Input: Speed ~ whatever it takes (within \$ reason) to net the above output ;

1750 rpm 3 phase 240v motor controlled by a 1 phase 115v source like an AC Tech controller.

NOTE: NONE of the items have been spec'd yet. The above noted motor came from a dual-drive worm system suggestion for the above noted output.

Someone suggested that PLASTIC gears are possible here. (??)

How do I compute the HP of the required motor?

"White" paper on this subject ~ where, pls.

Does a planetary gear sysetm make sense here -or- a multi-stage worm drive?

Regards, Wayne

• posted

"Wayne G. Dengel" wrote in news:QYHNg.11753\$OI1.10726@trnddc05:

Double-reduction worm drive, 400:1 gives you 4.25 RPM from a 1750 motor and would definately be self-locking. Call Boston Gear.

• posted

But can this be done with a planetary system?? Already have cost details for a dbl-reduction worm

Wayne

• posted

Given the desired torque and desired rotation rate, the required HP is already defined except for any inefficiency in gearing the motor to the desired rpm.

For the system of units you specify, 2500 lb-in at 4 rpm, all that's needed for HP is the scaling factors. I'll do it from basic principles. for fun.

pick a point one inch from the center of a shaft - a force of 2500 lb is moving at 4 rpm, which is a distance of 2 pi X 4 inches per minute.

2500 lb = 2500/2.2 kg = 2500 X 9.81/2.2 newtons 8 pi inches/min = 8 X pi / (39.37 X 60) meters/sec

newton X meters/sec = power in watts power in watts/746 = power in HP

Hence (2500 X 9.81 / 2.2) newtons X ( 8 X pi) / (39.37 X 60 X 746) meters/sec X HP/watt =

0.2 HP (rounded up)

It may be hard to find a 3 phase 240 volt motor that small. To reduce 1800 rpm to 4 rpm a reduction ratio of 450:1 is needed. Too much for one stage. How about two worms and pinions in series? Around 21:1 each

Thats a motor shaft worm driving a 21 tooth pinion. The worm attached to this pinion shaft drives a second pinion of 21 teeth on the output shaft. Not very efficient - but do you really care?

btw - "reversable" could mean you want the output to back drive the input - which it won't: it's "self-locking" for practical purposes.

Brian Whatcott Altus OK

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"Wayne G. Dengel" wrote in news:ZNZNg.9328\$Rw2.1708@trnddc02:

I've never seen a planetary with that much reduction.

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